The present invention relates generally to video signal processing apparatuses for processing video signals at the time of a special reproduction mode, and more particularly to a video signal processing apparatus which carries out a digital signal processing to compensate for a deterioration in the signal-to-noise (S/N) ratio of a reproduced video signal that occurs when a reproducing element traverses one track from another track during a special reproduction mode of a recording and reproducing apparatus such as a helical scan type video tape recorder (VTR), which special reproduction mode is a mode in which recorded signals are reproduced from a pre-recorded recording medium by moving the recording medium at a such speed that a relative speed between the reproducing element and the recording medium is different from the relative speed at the time of the recording or by stopping the recording medium.
As is well known, a helical scan type VTR may assume a special reproduction mode in which recorded signals are reproduced from a pre-recorded magnetic tape at a speed which is different from the speed with which the magnetic tape is moved at the time of the recording or by stopping the magnetic tape. During such a special reproduction mode, a relative speed between the magnetic tape and a head differs from the relative speed at the time of the recording, and thus, the slope of a scanning locus of the head becomes different from the slope of the pre-recorded track formed on the magnetic tape. For this reason, when the special reproduction is carried out with respect to a pre-recorded magnetic tape having such a track pattern that two mutually adjacent tracks are formed by rotary heads having gaps of mutually different azimuth angles and no guard band or only an extremely narrow guard band is formed between the two mutually adjacent tracks, a reproducing rotary head which is carrying out the reproduction during one track scanning period alternately traverses a pre-recorded track formed by a rotary head having a gap of the same azimuth angle as that of the reproducing rotary head and a pre-recorded track (reverse track) formed by a rotary head having a gap of an azimuth angle different from that of the reproducing rotary head. When the reproducing rotary head scans over the reverse track, the level of the reproduced signal greatly decreases due to the azimuth loss effect, and the S/N ratio of the reproduced signal becomes deteriorated.
Similarly, during a special reproduction mode of a helical scan type VTR which does not employ the azimuth recording system, a reproducing rotary head scans over a pre-recorded magnetic tape having such a track pattern that a sufficiently wide guard band is formed between two mutually adjacent tracks, and the reproducing rotary head traverses the guard band one or more times during one track scanning period. Hence, the level of the reproduced signal greatly decreases when the reproducing rotary head scans over the guard band, and the S/N ratio of the reproduced signal becomes deteriorated.
In a case where the special reproduction mode is a frame advance mode in which a still picture is successively obtained from arbitrary tracks on the pre-recorded magnetic tape, it is necessary to carry out an accurate servo operation with respect to the tape moving mechanism so that noise appears outside the effective reproduced picture, in addition to taking measures to compensate for the deterioration in the S/N ratio of the reproduced signal. However, it is difficult to take such measures so that the noise appears completely outside the effective reproduced picture, and there is a problem in that some noise inevitably appears within the effective reproduced picture.